Supersonic nozzle



Sept. 24, 1963 Filed Jan. 19, 1962 W. J. ORLIN SUPERSONIC NOZZLE 4Sheets-Sheet I INVENTOR. WILLIAM J. ORLlN ATTORNEY AGENT Sept. 24, 1963w. J. ORLlN SUPERSONIC NOZZLE Filed Jan. 19, 1962 4 Sheets-Sheet 2 NJ*LIL Y Q INVENTOR.

WILLIAM J.0RLIN ATTORNEY Mm fl x,

AGENT Se t. 24, 1963 w. J. ORLIN 3,104,680

SUPERSONIC NOZZLE Filed Jan. 19, 1962 4 Sheets-Sheet 5 \=QIN\ #3 d a I 24 :21 A 3 8 4 Q w fi g m S O m INVENTOR. WILLIAM J. ORLIN ATTORNEY AGENTSept. 24, 1963 w. J. ORLIN SUPERSONIC NOZZLE Filed Jan. 19, 1962 4Sheets-Sheet 4 INVENTOR. WILLIAM J. ORLI N AGENT United States Patent3,104,680 SUPERSONIC NOZZLE William J. Orliu, Box 871, Dayton, OhioFiled .l'an. 19, 1962, Ser. No. 167,369 9 (Ilaims. (Cl. 138-45) This isa continuation-in-part application of my copending patent application,Serial No. 595,549, filed July 2, z195 6. This invention relates tosupersonic nozzles and, more particularly, to nozzles suitable for usein wind tunnels for controlling the flow Mach number variation toproduce uniform, shock free flow at supersonic speeds in such tunnels.

Examination of the prior art establishes the fact that a great diversityof supersonic nozzle configurations have existed for many years.However, all of these devices for converting the thermal energy of a gasinto flow energy at supersonic velocity have evolved from a single basicconcept-that of providing flow boundary Walls compatible with therequirements of theoretical gas dynamics. The aforementioned well knowntheory predicates a converging flow passage in which there are smoothcontour boundaries extending from the highest pressure region to aminimum area section (designated as the throat) and continuingdownstream therefrom as a di vergent passage in such manner that thecross section area continuously increases to a maximum value at theexit, while simultaneously providing the necessary boundary contourshape to properly'cancel all disturbances arising from this flowexpansion process. Thus, a supersonic nozzle will be useful for Windtunnel application only insofar as it succeeds in accomplishing theprocess just described, thereby providing a gas stream in the testregion of uniform velocity, pressure, and temperature. A number ofmathematical and graphical methods have been applied to the design ofsuch passages or channels and these have resulted in numerous mechanicalarrangements to achieve the calculated aerodynamic boundaries. Thegeneralized solutions fall into two main categories designatedtwo-dimensional or three-dimensional and characterized respectively byexpansion of the flow downstream of the throat in one plane only (x, y)or spatially (x, y, z coordinates); the former is illustrated by squareor rectangular nozzles having a pair of plane parallel opposite Wallswhile the latter is illustrated by conical or pyramid shaped nozzles(usually of square or round cross section). Further, both maincategories may be subdivided into variable or fixed types depending onwhether or not provisions are incorporated in the design to adjust theflow passage areas and hence obtain a series of aerodynamically correctnozzle shapes with a single mechanical contrivance; examples ofthree-dimensional variable nozzles include cylindrical rubber sleeveswhich are contorted to the desired shape by means of multiplescrew-jacks or tension bands, and plug designs which axially translate arigid contoured body to alter the flow area; two-dimensional variablenozzles are exemplified by contoured walls comprising combinations ofrigid and flexible segments ranging from entirely flexible (or spring)walls formed to shape by jacks, to entirely rigid contours which areeither pivoted or translated with respect to each other.

Heretofore, variable supersonic nozzles, both automatic and manual, havebeen employed in wind tunnel facilities for some time. Two importantadvantages of such nozzles, multiple Mach number testing with a giventest setup and greatly increased facility utilization, quickly ofisetthe relatively high initial cost of the adjustable nozzle installation.However, it is apparent there can be no significant compromise witheither reliability of operation or aerodynamic quality of flow.

The two types of adjustable nozzles used in major wind tunnel facilitiesare the asymmetric sliding block nozzles and the completely flexiblewall nozzles. In the former type, Mach number variation is obtained bychanging the relative position of two fixed contours. The wall shapes ofthe fixed contours are correct for two Mach numbers only, althoughexperimental results indicate that satisfactory flow may be obtained atintermediate values and, also, slightly above and considerably below thedesign range. However, this type of nozzle is very much longer thansymmetrical nozzles because all expansion waves originate on one Walland all cancellation is accomplished on the other wall. Also, aformidable problem is introduced in free jet application because of jetexit dissymmetry resulting from translation of the nozzle block.

The latter type of nozzle offers the possibility of obtaining therequired nozzle contours at all Mach numbers and under all flowconditions. In this type the plate thickness and jack spacing are fixedby the maximum allowable slope between jack stations consistent with therequired flow quality. If the number of jacking points and hencemechanical complexity are kept to a minimum, the flexible plate must hethick, with the result that the minimum allowable bending radius (andtherefore nozzle length) is increased. Manufacturing, control andcalibration problems associated with the completely flexible nozzle arecomplicated; the possibility of mechanical or electrical failure leadingto permanent distortion of the flexible Wall is ever present. It is alsopossible that considerable loss of operating time might result becauseof minor control system difliculties. It is apparent, therefore, thatthe former type of nozzle is characterized by compromising aerodynamicsand simple control, while the latter type of nozzle presents complicatedcontrol and good aerodynamics.

The purpose of the present invention is to provide a symmetrical,supersonic nozzle that offers combining of good flow quality, i.e., Machnumber and flow direction, and simple control.

The supersonic nozzle constructed according to the present invention isfurther adapted to be employed in connection with supersonic windtunnels for free jet testing of air breathing engines, and is, also,adapted to provide continuous and rapid variation of Mach number fortransient testing over a broad range.

The present invention further provides a nozzle with a symmetricalnozzle exit configuration at all Mach numbers to avoid jet boundarydisturbances in the region of the air breathing engine inlet and with ashort nozzle length to permit angle of attack variation which isespecially necessary because of the impracticability of pitching thetest engine to high angles of attack.

The present invention specifically relates to two-dimensional variablenozzles and, more paiticularly, to the type which employs 'com'b-inedrigid and flexible Walls to attain flo-w passage area variations. Thereis presented a completely new principle of operation and mechanism forattainment thereof. Said principle utilizes a contour generating unit(movable Wall) consisting of a formed rigid upstream portion (designatedas scoop inlet segment) and an integrally attached flexible platedownstream portiton arranged in such manner that as the scoop inletsegment moves in circular arc motion about a fixed pivot point, therebychanging the throat area, the flexible plate automatically elasticallydeforms in accordance with the required aerodynamic cancellation shape.The aforementioned arrangement refers to the pivot point location andflexible plate end conditions (both upstream and downstream extremities)which are exactly defined by the design methods of this invention andtherefore not amenable to arbitrary disposition. Thus, variation of exitMach number is achieved solely by rotation of the scoop inlet segmentabout a fixed center without any requirement for screw-jacks or othercomplicated positioning devices on the flexible plate. For simplicity ofex )lanation, the above description or" the operating principle of thepresent invention mentions only one contour gen erating unit since anozzle may be so constructed (having -a third plane Wall perpendicularto the two plane parallel opposite walls); however, it is to be clearlyunderstood that the invention primarily relates to a configurationemploying two identical con-tour generating units symmetrically disposedabout a centerplane and moving simultaneously toward and away from eachother; this latter configuration is solely referred to in the inventionapplication since, in view of the above, it also embraces the reflectionplane (single contour generating unit) design.

The nozzle of the present invention is also characterized by itssymmetry of flow for the possibility of flow angularity deviation isminimized since geometric symmetry is maintained throughout theoperating range, and is further characterized by its minim-um lengthsince the flexible wall section or plate origin-ates at or downstream ofthe inflection point of the nozzle wall curvature and therefore thethroat section curvature and initial expansion are dictated byaerodynamic considerations only.

Also, the present invention provides a supersonic nozzle in which thepivot point location of the rigid walls and the flexible wall sectionend conditions may be obtained by several convenient papa-meters thatoptimize the nozzle wall contours during calibration.

The nozzle of the present invention is further characterized by itssimplicity of control which is obtained solely by symmetrical rotationof the scoop inlet segments about their pivot by a single power actuatoror mechanism connected thereto.

These and other features of the present invention are described indetail below in connection with the accompanying drawings in which;

FIG. 1 is a diagrammatic showing of a contour generating unit of thetype utilized with the invention;

FIG. 2 is a diagrammatic showing of a nozzle embodying the presentinvention;

FIG. 3 is a longitudinal sectional view partly in elevation showing anozzle embodying the present invention positioned in a wind tunnelsection;

FIG. 4 is a schematic top plan view of the nozzle of FIG. 3;

FIG. 5 is a fragmentary enlarged transverse section of the nozzle takensubstantially on line 55 of FIG. 3; and

FIG. 6 is an enlarged end elevation of the nozzle of FIG. 3.

Referring now in detail to the drawings wherein like numerals designatelike parts throughout the several views, there is generally illustrat dat 1d the contour gencrating-unit of the invention which unit includesseveral distinct components which in their specific relationship definean improved composite unit forming the basis of the invention, and whentaken together with an actuation meohanism (hereinafter described)comprises a completely new automatic supersonic nozzle system. Thusreferring to FIG. 1, the airflow surface of the contour generating unitIt consists of an 'aerodyna-mically shaped rigid portion or scoop inletsegment 12 and a flexible portion or flexible plate 18 shown integrallyformed from a solid block of metal (since this is desirable from thestructural viewpoint). Securely attached to the scoop inlet segment 12are the pivot arm 54 with sidewise projecting shaft 56 and wiper seal 86while at the downstream end of the flexible plate 18, slidable supportmeans are provided at 58. The overall nozzle configuration, therefore,consists of two such. contour generating unit assemblies as shown inFIG. 2 symmetrically arranged about the centerplane AA and which may becontained in a box-like structure (as will be described hereinafter) sothat there is minimum clearance between the movable walls (constitutingsegments 1") and the two plane parallel opposite side walls which, aspreviously discussed, are

characteristic of the two-dimensional type nozzle; also it is to benoted here that the box enclosure is pressure-tight and that the top andbottom of said enclosure also serve as mounting bases for mechanismcomponents which engage the flexible slidable support means 58 and thewiper seal 86. The method of operation by which the contour generatingunits or movable Wall assemblies generate rethe flexible plate juncturepoint P. However, the down 1 stream extremity of the flexible plate 13is constrained to move in an axial direction only (parallel tocenterpl'ane AA), and, therefore, the slope and ordinate will remainunchanged. Now, it can be shown by mathematical analysis that (for smalldeflections within the elastic theory) the slope and ordinate at bothends of a flexible plate are sufflcient to completely define thegenerated smooth curve. The present invention utilizes this naturalplate bending property through selection of the geometrical parametersof pivot point location (which determ nes motion of point P) and lengthof flexible plate 13 in such manner as to obtain coincidence between thegenerated elastic shape and the required aerodynamic contour throughoutthe operating range. The necessity for slidably supporting thedownstream end of flexible plate 18 at 58 is apparent since point P isdisplaced axially when moving in a circular are about the pivot, and theprojected length of the lexible plate is dependent upon the generatedcurve; the combined effect is to cause the flexible plate end at 58 tomove in a downstream direction as the throat is closed (i.e., scoopinlet segment rotates toward centerplane). Further, the wiper seal 35acts as an essential component of the movable wall assemb-ly since itserves in conjunction with a mating member of the enclosed boxstructure) to prevent high pres sure air leakage into the region behindthe flexible plate, irrespective of the angular position of the scoopinlet segment 12. In the diagrammatic view of FIG. 2, the nozzle boxframe 2? is shown with one side wall removed and with the symmetricalpair of contour generating units at 12 in a high Mach number operatingposition; it is evident that additional angular motion would cause theupper and lower scoop inlet segments 12 to come into contact at thecenterplane A-A thereby closing the throat, while rotation in theopposite direction effects a progressively open throat reaching a limitof operation cone spending to a straight flexible plate condition(utilized for the lowest design Mach number).

Referring to the drawings and in detail to the several components of theinventive contour generating unit 10', thEIE 'EllIC described hereincertain additional important features which are essential to the overalloperation of the invention. The component constituting the scoop inletsegment 12 for-ms the rigid upstream portion of the inventive contourgenerating unit It} and extends across the full width of the air passageperpendicular to the plane parallel opposite walls of the box frame 28mounting said contour generating unit 19. One of said walls isillustrated at 23 in FIG. 2-; said component 'isfreely movable betweensaid parallel walls having its edges in the closest possible proximitythereto without actual rubbing contact. The airflow surface of the scoopinlet segment 12 is contoured in such manner as to provide a gradual,loss-free transition from the very low subsonic entrance velocity of thegas stream to the supersonic Each angular position of the scoop velocityat the start of the flexible plate 18; thus, as shown in FIG. 2, allangular positions (identical for upper and lower scoop inlet segmentssince these are synchronized by an external drive system) will resu t insimultaneous formation of a convergent passage 1-!- and a divergentpassage 16. Although not specifically limited thereto, theaforementioned airflow contour of the scoop inlet segment 12 isgenerally a continouus composite curve consisting of a circular arcupstream lip, an ellip tical segment which extends to the vicinity ofthe throat region, and a downstream portion defined by a cubic (orhigher order) equation. This latter portion of the surface contour ofsegment 12 is of particular importance in the design method since thesupersonic expansion waves originate thereon and consequently determinethe flexible plate bending curves necessary for complete uniform flow atthe exit; two distinct design variations are herein presented and, inconstnuctin a nozzle embodying the subject invention, the selection ofone or the other will be established by the desired Mach numberoperating range. If the desired range includes sonic velocity (Machnumber 1.0) and does not exceed approximately Mach number three, theoptimum design configuration would be one in which the curve defined bythe cubic (or higher order) equation extends to the downstream tip ofthe scoop inlet segment 12, having zero curvature at this point (pointP, FIG. 1) and being convex to the flow along its entire length; theflexible plate originates at this tip (matching ordinate and slope atthe airflow surface) and, for values of Mach number greater than unity,would present a concave airflow surface thereby causing an inflectionpoint to exist at the juncture of scoop inlet segment 12 and flexibleplate 21$. The second design variation applies when the desired Machnumber range is entirely supersonic, and results in an optimumconfiguration for which the expansion curve terminates at a definitedistance (depending on the design range) upstream of the flexible plateoriginagain, the expansion curve is arranged so that the curvature iszero at the terminal point and the surface is convex to the flowupstream therefrom; however, in this instance, an additional cubic (orhigher order) curve (determined by theoretical supersonic flowcharacteristics methods) is provided between said terminal point and thedownstream tip of the scoop inlet segment 12, disposed in mannerdirectly opposite to the first curve but continuous therewith (i.e.,matching slope and ordinate, concave to the airflow, and having zerocurvature at its upstream end) thereby causing an inflection point toexist on the surface of the rigid contour at the merging point of theaforementioned curves; the flexible plate will originate at point P(FIG. 1), matching the slope and ordinate of the terminal curve justdescribed, and will thus present a continuous concave airflow surfacedownstream of the inflection point. In summary, the airflow surfacecontour of the scoop inlet segment 12 as well as the general overallproportions of the contour generating unit it) are fundamentallyestablished by the intended Mach number range of the nozzle. Utilizationof the scoop inlet configuration of this invention provides excellentsubsonic airflow velocity distribution in the contraction region l tthereby contributing significantly to achievement of uniform, shock freesupersonic gas flows; the projecting upstream lips or" the scoop inletsegments 12 allow favorable streamline adjustment and attachment of theapproaching airflow, thus avoiding possible separation and otherundesirable effects normally associated with intake of the thickboundary layer existing on the plenum inlet walls. An additional veryimportant advantage is realized as a consequence of the symmetricalangular movement of the scoop inlet segments 12 since, as the opposingairflow contours approach one another (throat closing), the minimum areaplane continuously relocates in an upstream direction to provide alonger supersonic 6 expansion region as is inherently required by gasdynamics theory.

The flexible plate components 18 of this invention are arranged toautomatically bend (within the elastic range of the metal) in suchmanner as to provide identical but opposite (mirror images about thecenterplane A-A) continuous concave airflow surfiace contours compatiblewith each value of the throat height (and hence nozzle exit Mach number,since the exit height remains constant), said required airflow surfacecontours for each Mach number being determined by well known theoreticalgraphical-analytical methods. Automatic bending of the flexible plates18 is accomplished solely by rotation of the scoop inlet segments 12about the pivot shaft centers 56, thus completely eliminating the needfor jacks or other devices affixed to said plates intermediate of theirends. As noted previously, each flexible plate 18 is rigidly attached atits upstream end to the respective scoop inlet segment (preferablymachined integral therewith) forming a smooth continuation of theairflow surface thereon; hence, angular displacement of the scoop inletsegment 12, which is constrained to move in a circular path by the pivotarm 54 securely attached thereto, results in the flexible plate originpoint P (FIG. 1) describing a portion of a circular arc with radiusequal to the distance between point P and the center of respective pivotshaft 56. Further, the downstream end of the flexible plate has anintegral rigid block formed thereto, as indicated at 18a, said blockbeing slidably supported to move parallel to the centerplane A-A only asby means of slidable support means 58, thereby causing the slope andordinate (distance from the centenpl ane AA) of the downstream extremityof the flexible portion of plate 18 to remain fixed while allowingunhindered longitudinal mo tion (of this extremity) as the scoop inletsegments -12 pivot on the shafts 56. Now, by applying the theory forelastic bending of thin, constant thickness plates, it is found that theabove-described arrangement for restraint of the ends of flexible plate18 will result in continuous curves, everywhere concave to the airstream and properly shaped, as required by the aerodynamic design,providing the length of flexible plate 18 and scoop inlet segment pivotpoint location are properly selected; exact selection of theseparameters is dictated by the desired Mach number operating range of thenozzle. In general, the pivot point must be located so that the flexibleplate 18 will be straight (and parallel to the centerplane A-A) for thelowest value of Mach number in the design range and, further, must belongitudinally confined to the middle third of the flexible platelength; this latter condition is theoretically necessary to preventoccurrence of an inflection point intermediate of the flexible plateends. In the above description, the flexible plate was assumed to be ofconstant thickness throughout its length and such configuration has beenfound to be entirely satisfactory in practice; however, this restrictionis not required since the design method can be extended to includelongitudinally tapered (and other) plates when some advantage mightaccrue. Referring again to the constant thickness design, the actualvalue employed will be determined by the maximum operating pressurelevel and the allowable yield stress of the metal. In summary, theflexible plate 18 of this invention is rigidly attached to thedownstream tip of the scoop inlet segment 12, contains an integral block18a at its downstream extremity which is slidably supported at 58 fromthe nozzle box enclosure, and is completely devoid of jacking or other Ipositioning devices intermediate of its ends; the exact overall lengthand thickness are determined by the operating requirements (principally,Mach number range and maximum pressure). Said flexible plate 18 iscaused to bend elastically solely by controlled angular displacement ofthe scoop inlet segment 12 about the pivot 55; proper location of saidpivot center results in elastic bending curves which precisely match therequired theoretical aerodynamic contours. Further, as discussedhereinafter, the pivot shafts 56 serves an additional primary functionof structural aspect, being the means of transmitting the very highlongitudinal pressure forces (which exist on the adjustable surfaces ofall variable nozzles) into the enclosing box structure; since the pivotshafts 56 are mounted in high capacity anti-friction bearings, thecontour positioning actuation mechanism to be utilized therewith iscompletely relieved of loading from the aforementioned source.

The wiper seal 36 provides a gas seal in the chamber of the inventivenozzle at the nozzle inlet in order to prevent application of the highpressure therein to the underside of the flexible plate 18. Said seal isrigidly attached to the underside of the scoop inlet segment 12 andextends full width thereof and contains a smooth, curved downstream face86:: which is a portion of a circular arc having its center coincidentwith that of the pivot shaft 56. Engaging this seal face 36a is a wiperplate 88 (with suitable pressure packing material in its upstream edge)fastened to the nozzle box enclosure 28 and extending fully between theopposite parallel side walls thereof. The seal thus formed isindependent of the angular position of the scoop inlet segment 12 duringactuation thereof about the pivot center 56. An equally importantfunction of the wiper seal component 86 is associated with its effect onaerodynamic forces as follows: The contour generating unit 14? issubjected to pressure forces induced by the airflow; the pressure in theflow passage 14-46 decreases continuously from the scoop inlet lip tothe nozzle exit, whereas the reverse side of the contour generating unitltl experiences the highest system pressure in the region upstream ofthe wiper seal face She and a very low value downstream therefrom.Integration of these surface pressures over the entire perimeter of thecontour generating unit it) yields a resultant force and moment at thepivot shafts 56; the force is transmitted directly to the nozzle boxenclosure 28; however, the moment resulting therefrom is applied to theactuation mechanism. The desirability of minimizing said momentthroughout the operating range is obvious, and this can be effectivelyaccomplished by judicious longitudinal location of the wiper seal 86 andrelated wiper plate 83.

The previously-referred to actuating mechanism may include an externaldrive mechanism for actuating the scoop inlet segments 12 in symmetricalmotion toward and away from one another thereby generating the requiredsupersonic nozzle airflow passages. It is evident that numerous suchmechanisms can be utilized. For example, separate hydraulic cylinderactuators (one for each contour generating unit) could be attachedbetween the underside of the scoop inlet segment 12 (adjacent to theseal plate) and the nozzle box enclosure 28, being operatedsynchronously by suitable controls. Again, actuation might beaccomplished solely through the pivot shafts 56 by having said shaftsextend through one of the box enclosure side walls and affixing thereona synchronized power driven gear system. Thus, the specific choice ofactuating mechanism will depend largely on the particular nozzleapplication. However, a precise micro-adjusting type system, suitablefor high pressure nozzle operation, is described in detail hereinafterand forms part of the subject invention. It is important to note herethat said mechanisms all reflect the inherent simplicity of the contourgenerating unit operating principle of angular motion about a fixedcenter; as a consequence, and especially in view of the pressurebalancing action of the wiper seal 86, a supersonic nozzle constructedaccording to this invention will permit extremely rapid traverse of theMach number range, thereby providing transient test capabilities notheretofore available.

FIGS. 3 and 4 illustrate a practical stnuctural arrangement of thesupersonic nozzle embodying the present invention, wherein the nozzlehas been mounted in a test chamber of a wind tunnel for operation. Thecontour generating units 10 of the nozzle are arranged in vertically.

spaced relation between two fixed side plate Walls 22, 23 havingparallel surfaces. A top plate Wall 24 and a bottom plate wall 2%extending between and connectcdto the side walls 22, 23 form a rigid boxframe 28 for supporting the contour generating units 10 in the testsection 29.

At the upstream end of the box frame 28, the side plate walls 22 and 23are formed with curved end edges and are further arranged to abutfairing plates 30 mounted in the wind tunnel test section 20 and rigidlyheld in place by base plates 32 bolted to the fairing plates 30' and tothe walls of the test section 20 as by bolts 36 as shown in FIG. 3. Atthe downstream end, the box frame 28 is arranged to extend through anopening 38 in a bulkhead 4% of the test section 29, and on whichhulkhead 4% the box frame 28 is pivotally mounted by pins 4-2 extendingthrough lugs 44 and pivotally engaging the or decreasing the angle ofattack of the nozzle, particularly useful in testing jet engines or thelike. The top and bottom walls 24 and 26 of the box frame 28 are furtherprovided with seal blocks 48, which blocks 48 are aligned with thebulkhead opening 38 and are formed with a curved surface 54 arranged toengage seal plates 52' attached to the bulkhead 49 thereby sealing offthe test section 2i) and, therefore, preventing any fluid flow throughthe opening 38 around the outer surfaces of the box frame 28 to spoilthe fluid flow at the exit of the nozzle.

The walls 10 of the nozzle are further provided with arms 54 attached tothe scoop inlet segments 12 pivotally mounted on the side walls 22, 23as at 56 for pivotally supporting the scoop inlet segments 12 forrotational movement to various positions, for example, such a positionas shown by the dotted line in FIG. 3, for obtaining Mach numbervariations. The flexible wall sections 18 of the contour generating unit10 are slidably supported by rollers 58 at the downstream ends thereof,which rollers 53 engage tracks 66 provided on the inner sides of the topand bottom walls 24, 26, respectively, of the box frame 28, as shown inFIGS. 3 and 6.

It is apparent, therefore, that longitudinal flexing of the flexiblewall sections or plates 18 is obtained by the simple rotational movementof the scoop inlet segments 2 about the fixed pivot centers 56, whilethe free ends of the flexible wall sections '18 are slidably guided bythe rollers 58 in the tracks 60.

Rotation of the nozzle walls 10 about their pivot centers 56 for asimultaneous positioning thereof to a wide range of settings forcontinuous Mach number variation control is obtained by a single poweractuator 62 consisting of a pair of drive lead screws 64 mounted on theouter side of the side plate walls 22 and 23 as shown in FIGS. 4 and 5.As shown in detail in FIG. 5, each lead screw 64 formed with an upperright hand and a lower left hand threaded portion is arranged to bedriven by either manual means (not shown) or by a motor 66 through agearing system 68 arranged in any well known manner.

Each drive lead screw 64 is further provided with a pair of internallythreaded slides 70 arranged for simultaneous movement toward and fromone another by rotation of the drive lead screw 64. The slides 70 arefurther connected to a pair of slide blocks 72 by pins 74 extendingthrough openings 76 in the side wall 22 for movement of the slide blocks72 with the lead screw slides 70. The slide blocks 72 slidably arrangedbetween the side walls 22 are connected to their respective scoop inletsegments 12, for movement therewith by pins 78 extending throughopenings in the slide blocks 72 and through openings in arms 80 fixedlyattached to the scoop inlet segment 12 as shown in FIG. 5. The leadscrews 64 are, also, synchronized by idler gears 82 only one of which isshown as in FIG. 5.

In order to prevent air leakage from the sides of the nozzle, the edgesof the contour generating unit abutting the fixed side plate walls 22,23 and the fairing side plates are formed with grooves that function aslabyrinth seals 84 providing minimum clearance with the inner surfacesof the side walls 22, 23 and the fairing plates 30. In addition, thewiper seals 86 attached to the contour generating unit similarly employlabyrinth seals along their. edges and provide minimum clearance on theinner surfaces of the fairing plates 30. Also, the wiper sealsfrictionally engage seal plates 88 attached to the upstream edges of theside plate walls 22, 23 as shown in FIG. 3. Air leakage is thereforeprevented by sealing along all the moving parts of the nozzle as justset forth above. Also, the nozzle walls 10 may be provided with sidespacing rollers 90 mounted on the sides of the scoop inlet segment 12 asshown in FIG. 3.

The specific mechanism and arrangements have been described above forpurposes of illustration only and the present invention is not intendedto be limited by this description or otherwise except as defined in theappended claims.

I claim:

1. A symmetric supersonic nozzle comprising a pair of walls arranged inspaced relation defining a fluid flow passageway, said walls each havinga rigid section incorporating a scoop inlet and a pivot center extendingfrom a point adjacent the upstream end of said passageway downstream toa flexible section integrally formed at its upstream end with said rigidsection and terminating in a slidably supported downstream end, saidwalls having predetermined curvatures each characterized by aninflection point formed upstream of the juncture between said rigid andflexible sections and forming a subsonic contraction and a supersonicexpansion section in said passageway, and a single power mechanismconnected to said rigid wall sections for simultaneously moving saidwalls toward and from one another for varying the crosssectional area ofsaid sections thereby controlling the Mach number variation of the fluidflow, said single power mechanism comprising a pair of drive lead screwelements integrally formed in spaced relation to each other andincorporating, respectively, right hand and left hand threaded portions,an internally threaded slide element in adjustable engagement on each ofsaid pair of screw elements for simultaneous movement toward and fromeach other on rotation of said drive screw elements, a slide blockelement pin-connected to each of said slide elements for movementtherewith and an arm element affixed to each of said walls andpin-connected to each of said slide block elements for movement of saidwalls towards and from one another on simultaneous operation of saidpair of drive lead screw elements.

2. A variable nozzle suitable for producing uniform, shock free fluidflow at supersonic speeds comprising a pair of fixed parallel walls, apair of movable rigid walls of preshaped contour arranged in spacedrelation, defining with said fixed walls a fluid flow passageway ofvarying cross section, said rigid walls each incorporating an inflectionpoint and being of preshaped contour forming upstream curved innersurfaces, and a pair of flexible walls extending from said rigid wallsfrom a point originating at or a predetermined distance downstream fromthe inflection point, said rigid Walls arranged for pivotal movementtoward and from one another, and said flexible walls integrally formedwith, and as a continuation of, said rigid walls, said flexible wallseach terminating in a downstream end portion slidably positionedrelative to said fixed parallel walls and accordingly arranged forautomatic flexing compatible with pivotal movement of said rigid wallsthereby forming downstream flow surfaces with a reverse curvature withrespect to the upstream flow surfaces for achieving uniform fluid flowin said nozzle and control means for effecting pivotal movement of saidrigid walls towards and from one another thereby simultaneouslyautomatically flexing said flexible walls, said control means comprisinga pair of oppositely threaded relatively elongated power-actuated maincontrol elements arranged for simultaneous movement in oppositedirections, pin-connected interconnecting elements operatively connectedbetween each of said pair of main control elements and each of said pairof walls for effecting simultaneous pivotal movement of said wallstowards and from each other, said variable nozzle adapted for mountingwithin a wind tunnel having fixed, parallel side wall surfaces, and topand bottom wall surfaces extending therebetween and interconnected withsaid side wall surfaces to form a rigid box-like structure housing saidnozzle in supported relation therewithin, additional pivot means at thedownstream end of the wind tunnel pivotally mounting the downstream endof said box-like structure, and means for pivoting said box-likestructure and the nozzle carried therewithin to a variety of angularlyrelated positions corresponding to a plurality of angles of attack.

3. A variable transonic nozzle having a pair of fixed and parallel sidewalls enclosed within top and bottom walls, said nozzle comprising apair of spaced rigid walls housed within said fixed walls defining thefluid flow passageway, said rigid walls having a curved inlet sectionand an outlet section of similar curvature forming a continuous convexsurface, a pair of flexible walls integrally attached to said rigidwalls forming a concave downstream extension thereof and establishing apoint of inflection at the juncture of the rigid and flexible walls,said rigid walls incorporating integrally attached arms pivotallysupporting said rigid walls on said fixed walls at pivots located inpredetermined manner intermediate of the ends of said flexible walls,and said flexible walls slidably supported at the downstream endsthereof on said fixed walls, whereby said rigid walls may be rotated formovement toward and from one another thereby flexing said flexible wallsto form the desired aerodynamic curvature, and power actuated means formoving said combined rigid and flexible walls pivotally toward and fromone another.

4. A variable supersonic nozzle having a pair of fixed and parallel sidewalls enclosed within top and bottom walls, said nozzle comprising apair of spaced rigid walls housed within said fixed walls defining thefluid passageway, said rigid walls having a curved inlet section and anoutlet section of reverse curvature with respect to said curved inletsection forming a point of inflection therebetween, a pair of flexiblewalls integrally attached to said rigid walls forming a downstreamextension thereof beginning at a point originating a predetermineddistance downstream of the point of inflection, said rig-id wallsincorporating integrally attached arms pivotally supporting said rigidwalls on said fixed walls at pivots located in predetermined mannerintermediate of the ends of said flexible walls, and said flexible wallsslidably supported at the downstream ends thereof on said fixed walls,whereby said rigid walls maybe rotated for movement toward and from oneanother thereby flexing said flexible walls to form the desiredaerodynamic curvature, and power actuated means for moving said combinedrigid and flexible walls pivotally toward and from one another.

5. A two-dimensional variable supersonic nozzle including a contourgenerating unit comprising a rigid scoop inlet segment, a pivot armrigidly attached to the downstream end of said scoop inlet segment,transversely extending pivot shaft means pivotally supporting the end ofsaid pivot arm for pivotal movement of said scoop inlet segment about afixed center, a flexible plate rigidly attached at the upstream endthereof as a continuation of said scoop inlet segment, and slidablysupported rigid block means on the downstream end of said flexible platefor movement in a direction parallel to the centenplane of said nozzle,said contour generating unit having a box enclosure for supporting saidpivot shaft means in fixed relation thereto, a Wiper plate aflixed tosaid nozzle box enclosure and extending transversely between oppositeside walls thereof and wiper seal means aflixed to the underside of saidscoop inlet segment and incorporating a smooth downstream face portionconstituting a portion of a circular arc having its center of radiuscoincident with that of said pivot shaft means and in continual,pressure-sealing contact with said Wiper plate independent of theangular position of said contour generating unit to thereby preventapplication of high pressure upstream thereof to the underside of saidflexible plate, said scoop inlet segment and wiper seal arrangementconstituting means, through proper longitudinal positioning of saidwiper seal means, for balancing aerodynamic loads on said contourgenerating unit.

6. A two-dimensional variable nozzle comprising a pair of contourgenerating units each including a scoop inlet upstream portion, aflexible, relatively elongated downstream portion atlixed to saidscoopinlet portion and terminating in a slida bly supported end, a box-typeenclosure for supporting said contour generating unit in pressure-sealedrelation, transversely-disposed pivot means afiixed between oppositeside walls of said enclosure incorporating pressure sealed plate meansextending fully thereacross, interconnecting pivot arms aflixed to saidtransversely-disposed pivot means and aflixed at the upstream endthereof to the downstream end of said scoop inlet portion, and means forsimultaneously moving said scoop inlet portions in an are about saidfirst-named pivot means to move the point of juncture between said scoopinlet portion and said flexible portion constituting the origin of saidflexible portion in a circular are about said pivot means, and wiperseal means affixed to the underside of said scoop inlet portion incontinuous transverse relation thereacross and incorporating an arcuatesurface having a radius whose center is at the pivot means incontinuous, pressure-sealing relation with said pressure sealed platemeans for all angular positions of said contour generating unit.

7. A two-dimensional nozzle comprising a pair of identically contoured,relatively enlarged contour generating units arranged for angularmovement toward and away from a longitudinally extending center-plane,said pair of contour generating units including a pair of scoop inletsegments dis-posed in opposite relation to the centerplane and forming anozzle throat portion therebetween, a pair of flexible plate portions ofpredetermined length formed as a downstream continuation of said scoopinlet segments compatible with each change in throat height on openingor closing operation of said scoop inlet segments in relation to thecenterplane, said flexible plate portions automatically bending onrotation of said scoop inlet segments, a pair of pivot shafts positionedat a predetermined point downstream of the origin. of said flexibleplate portions and pivotally supporting said scoop inlet segments andincluding interconnecting arm elements aifixed to said pivot shafts andproviding constraint for said scoop inlet segments to limit the latterto movement in a circular path about said pivot shafts, rigid meansaflixed to the downstream end of said flexible plate portions anddisposed on opposite sides of the centerp-lane and ,slidably positionedfor movement parallel to the centerplane only to insure properaccommodation of elastic bending of said flexible plate portions inaccordance with and matching predetermined aerodynamic contours, and boxenclosure means having side wall surfaces enclosing said nozzle andproviding support for said pivot shafts.

8. A two-dimensional nozzle as in claim 7, and wiper plate meanspositioned on and extending rfu-lly across the width of said boxenclosure and a pair of Wiper seals attached to the bottom surfaces ofsaid contour generating units adjacent the scoop inlet segments thereofon the upstream end of said nozzle in contacting, pressuresealedrelation with said wiper plate means at all angles of adjustment of saidscoop inlet segments.

9. A two-dimensional nozzle asin claim 7, and actuating mechanism forsimultaneously operating each of a pair of said contour generating unitsforward and away from the closed and open throat conditions,respectively,

to provide automatic flexing of said flexible plate portions through therespective slidably positioned, rigid means attached to the downstreamends of said flexible plate portions.

References Cited in the file of this patent UNITED STATES PATENTS2,598,208 Bailey May 27, 1952 2,625,008 Crook Jan. 13, 1953 2,831,505Menard Apr. 22, 1958 OTHER REFERENCES Agardograph 3A summary of theTechniques of variable Mach Number Supersonic Wind Tunnel Nozzle Design,by J. T. Kcnney and L. M. Webb, October 1954 (TL 500 N6 No. 3),reference pages 4 and 78'79. (Copy in Patent Office Scientific Library.)

Agard (AG 15/ P6), Papers presented at the Fifth Meeting of the WindTunnel and Model Testing Panel,. Scheveningen, Netherlands AgardConference May 3-7, 1954 (TL WS N6p), reference pages and 146. (Copy inPatent Oflice Scientific Lbrary.)

3. A VARIABLE TRANSONIC NOZZLE HAVING A PAIR OF FIXED AND PARALLEL SIDEWALLS ENCLOSED WITHIN TOP AND BOTTOM WALLS, SAID NOZZLE COMPRISING APAIR OF SPACED RIGID WALLS HOUSED WITHIN SAID FIXED WALLS DEFINING THEFLUID FLOW PASSAGEWAY, SAID RIGID WALLS HAVING A CURVED INLET SECTIONAND AN OUTLET SECTION OF SIMILAR CURVATURE FORMING A CONTINUOUS CONVEXSURFACE, A PAIR OF FLEXIBLE WALLS INTEGRALLY ATTACHED TO SAID RIGIDWALLS FORMING A CONCAVE DOWNSTREAM EXTENSION THEREOF AND ESTABLISHING APOINT OF INFLECTION AT THE JUNCTURE OF THE RIGID AND FLEXIBLE WALLS,SAID RIGID WALLS INCORPORATING INTEGRALLY ATTACHED ARMS PIVOTALLYSUPPORTING SAID RIGID WALLS ON SAID FIXED WALLS AT PIVOTS LOCATED INPREDETERMINED MANNER INTERMEDIATE OF THE ENDS OF SAID FLEXIBLE WALLS,AND SAID FLEXIBLE WALLS SLIDABLY SUPPORTED AT THE DOWNSTREAM ENDSTHEREOF ON SAID FIXED WALLS, WHEREBY SAID RIGID WALLS MAY BE ROTATED FORMOVEMENT TOWARD AND FROM ONE ANOTHER THEREBY FLEXING SAID FLEXIBLE WALLSTO FORM THE DESIRED AERODYNAMIC CURVATURE, AND POWER ACTUATED MEANS FORMOVING SAID COMBINED RIGID AND FLEXIBLE WALLS PIVOTALLY TOWARD AND FROMONE ANOTHER.